nbc news white house correspondent. great to have that perspective. i want to bring in now from boylston street in boston, nbc's carey saunders who's out there in the cold. i understand police are still on the scene right now. what can you tell us about what things look like right there right now? >> reporter: well, it is is pretty much shut down. it will continue to be that way through into tomorrow. the reason that is, the authorities are treating this vast area as a crime scene. it's possible there may be a clue that is not quite obvious in the daylight, perhaps it will reveal itself. and so most of the access in and out is going to be restricted. there's a tremendous presence of police officers here. the boston police department is on alpha bravo shifts. that means officers are on 12 hours. when they go off, officers come on for another 12 hours and they're going to continue that for the nikts cext couple of da. the focus here is to find a suspect or suspects. ed davis, the police commissioner says anybody who believes there's a suspect is at brin